US President Donald Trump has said the White House Chief of Staff John Kelly will leave his job at the end of the year.Trump called Kelly "a great guy," while speaking to reporters at White House on Saturday, Xinhua reported."He's been with me almost two years now, between two positions," he said. "I appreciate his service very much."The US President said he would announce Kelly's successor "over the next day or two".Kelly, Trump's second Chief of Staff, took over the position from Reince Priebus in July 2017.Before that, he was the Trump administration's first Secretary of the Department of Homeland Security.